Recently, a mobile terminal embedded with a super small digital camera has been developed. A super small digital camera formed on a conventional mobile terminal is disadvantageous in that a gap between an image sensor adapted to change an outside light to a digital image or a digital picture and a lens cannot be adjusted. However, a lens driving device such as a voice coil motor adapted to adjust a gap between an image sensor and a lens has been recently developed to enable obtainment of an improved digital image or digital picture in a super small digital camera.
Generally, a voice coil motor is configured such that a lens is mounted therein, a bobbin arranged on a base is upwardly moved from the base to adjust a gap between a lens and an image sensor mounted on a rear surface of the base. The bobbin of the voice coil motor is coupled with a leaf spring to allow the bobbin to contact the base at all times by way of elasticity of the leaf spring when the voice coil motor is not operated.
That is, the bobbin of the conventional voice coil motor is driven only to one upward direction relative to the base. The conventional voice coil motor that drives to one direction relative to the base inevitably and disadvantageously needs a driving force larger than that of the elasticity of the leaf spring and a self weight of the bobbin in order to drive the voice coil motor, resulting in increased power consumption of the voice coil motor.
Another disadvantage is that size of a coil wound on the bobbin or a magnet is increased by a driving force larger than the self weight of bobbin and elasticity of the leaf spring to drive the voice coil motor, resulting in an increased overall size of the voice coil motor.
Still another disadvantage is that a focus between the lens and the image sensor is not precisely adjusted to degrade quality of an image, if the leaf spring is deformed.